Without throwing any type of equations out there (these would get very extreme very quickly...)I know from first hand experience (holding a rope attached to the ground) that a fully powered up 12 m2 kite @ 12 oClock can hold a 145 lb individual in the air with a 25 knot laminar wind.

Using basic static equations you can deduce that the kite is producing 145 lb of upwards lift.

Now what JRG is saying below with the tension gauge is a great idea to just directly test this. It could probably be rigged inline with the chicken loop and harness.

I gotta go back to work, but I hoping by the time I come back I realized the connection b/ wind energy vs air Reynolds #, foil efficiency, angle of attack, bridle curve, and lift to drag ratio so I can answer this in Layman's terms.

Someone should develop a system with tensiometers that can give precise information on forces on the lines and chicken loop. It could have it's own computer to store the data, and even include gps data on speed and height attained. This would make accurate comparison of kites more scientific.They could also be incorporated into footstraps to compare both impact and shear forces experienced between boards.Maybe someone is already using these in R and D?

I'd like to see power profiles for kites listed in the specs, so you can get objective data when shopping. Percentage depower when half and fully depowered would be helpful also to get an idea of a kite's range.We were kiting (barely) on a light wind day on a 12 Slingshot RPM, 12 RRD Obsession, and a 14 Naish Park. We're all around 200lbs, and the Park couldn't keep upwind as well. We switched kites just to be sure it wasn't rider/board variation. Obviously there's more to a kite's performance than power, such as responsiveness in turning and relaunch that can't be measured as easily. When the 14 Park was tested against a 13.5 RRD Obsession for relaunch in a light wind day, the RRD won hands down, and had significantly more power.P.S. Used 2011 14m Naish Park for sale: $400.

Also for hamstring (and larger muscle) recovery I recommend 'myofascial release' (http://en.wikipedia.org/wiki/Myofascial_release); or more specifically a foam roller (cyclist's best friend). Roll from the knee toward the glute while holding your upper body up, and for more pressure cross your other leg over and press down (there are probably pictures and more explicit instructions somewhere online). Works well before stretching, even better in conjunction with yoga. (I also use a 'stick' you can get at a runner's store but it works better on the quads and IT than the hams).